Different users require to exercise against different resistances, and the same user may require to exercise different sets of muscles at the same time, for example biceps and triceps. However triceps are only about 60% of the strength of biceps, and consequently an exercise machine having the facility to exercise both triceps and biceps desirably will offer resistance to movement of a user's arm in different degrees for forward and reverse movement for developing the respective sets of muscles. It is therefore the object of this invention to provide such a machine which will be simple, and which will be capable of easy adjustment.